This invention relates to Titanium alloys and, more particularly, to alloys containing Titanium, Vanadium and Chromium.
High strength Titanium alloys have been produced containing about 50% by weight of Titanium, up to about 35% by weight Vanadium, and up to about 15% by weight of Chromium. Some of these alloys contain trace and minor amounts of additives such as Silicon and Carbon and other elements. Such alloys are characterized by exhibiting a stable second phase in the microstructure and superior elevated temperature strength.
Conventionally, these high strength alloys are prepared by vacuum arc melting of an electrode made up of electron beam welded compacts of blended Titanium and preselected amounts of Vanadium and Chromium and other additions.
This vacuum arc melting process, while generally acceptable, has a major drawback where inclusions of undissolved Vanadium are sometimes found in the finished ingot. This condition cannot be eliminated successfully with stirring coils on the furnace or with as many as three or four successive vacuum arc remelts of the ingot. It is believed that the problem persists because the higher melting temperature of Vanadium in the presence of a significantly lower melting Titanium and Chromium alloy resists dissolution. Prior attempts to avoid this problem have included the addition of Vanadium in the form of thin chips to facilitate dissolution. While this reduces somewhat the frequency of occurrence of Vanadium inclusions, undissolved Vanadium was still encountered.
It is, therefore, an object of the present invention to prevent inclusions of Vanadium in the finished ingot or to substantially reduce the occurrence of Vanadium inclusions in high strength alloys containing Titanium, Vanadium and Chromium.
It is a further objective of the present invention to prevent the formation of a low melting Titanium-Chromium alloy during the production of a Titanium-Vanadium-Chromium alloys.